Travel to specific locations in Germany and Poland

I am new to the Community and am very much in need of advice with regard to travel by train to certain cities in Germany and Poland as part of a tour I plan for July 2023.  American Express no longer helps with train reservations and schedules so frankly I am rather lost.  This is to be a World War Two related tour to Berlin, Munich, Nurnberg, Berchtesgaden, Prague, Krakow, and Warsaw.  I already have a Polish guide for travel to certain locations by automobile, and have guides set up for Munich, Nurnberg, and Berchtesgaden, and am working on Berlin.  But I truly do not know how to even think about arranging for train travel between these destinations never having really traveled by train much in Europe before.  I am hoping that someone can help or knows a travel agent with whom I can work that can put together the itinerary for me.  Thank you.